- NetBSD Manual Pages
SSL(7) OpenSSL SSL(7)
Powered by man-cgi (2021-06-01).
Maintained for NetBSD
by Kimmo Suominen.
Based on man-cgi by Panagiotis Christias.
ssl - OpenSSL SSL/TLS library
See the individual manual pages for details.
The OpenSSL ssl library implements several versions of the Secure
Sockets Layer, Transport Layer Security, and Datagram Transport Layer
Security protocols. This page gives a brief overview of the extensive
API and data types provided by the library.
An SSL_CTX object is created as a framework to establish TLS/SSL
enabled connections (see SSL_CTX_new(3)). Various options regarding
certificates, algorithms etc. can be set in this object.
When a network connection has been created, it can be assigned to an
SSL object. After the SSL object has been created using SSL_new(3),
SSL_set_fd(3) or SSL_set_bio(3) can be used to associate the network
connection with the object.
When the TLS/SSL handshake is performed using SSL_accept(3) or
SSL_connect(3) respectively. SSL_read_ex(3), SSL_read(3),
SSL_write_ex(3) and SSL_write(3) are used to read and write data on the
TLS/SSL connection. SSL_shutdown(3) can be used to shut down the
Here are some of the main data structures in the library.
SSL_METHOD (SSL Method)
This is a dispatch structure describing the internal ssl library
methods/functions which implement the various protocol versions
(SSLv3 TLSv1, ...). It's needed to create an SSL_CTX.
SSL_CIPHER (SSL Cipher)
This structure holds the algorithm information for a particular
cipher which are a core part of the SSL/TLS protocol. The available
ciphers are configured on a SSL_CTX basis and the actual ones used
are then part of the SSL_SESSION.
SSL_CTX (SSL Context)
This is the global context structure which is created by a server
or client once per program life-time and which holds mainly default
values for the SSL structures which are later created for the
SSL_SESSION (SSL Session)
This is a structure containing the current TLS/SSL session details
for a connection: SSL_CIPHERs, client and server certificates,
SSL (SSL Connection)
This is the main SSL/TLS structure which is created by a server or
client per established connection. This actually is the core
structure in the SSL API. At run-time the application usually
deals with this structure which has links to mostly all other
Currently the OpenSSL ssl library provides the following C header files
containing the prototypes for the data structures and functions:
This is the common header file for the SSL/TLS API. Include it
into your program to make the API of the ssl library available. It
internally includes both more private SSL headers and headers from
the crypto library. Whenever you need hard-core details on the
internals of the SSL API, look inside this header file. This file
also includes the others listed below.
Unused. Present for backwards compatibility only.
This is the sub header file dealing with the SSLv3 protocol only.
This is the sub header file dealing with the TLSv1 protocol only.
Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
3.0.9 2023-05-07 SSL(7)